Legal And Other Proceedings (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2012
Proposed adjustment in income tax	$ 8.0
Minimum [Member]
Interest and penalties	6.0
Maximum [Member]
Interest and penalties	$ 10.0

Income Tax Examination Penalties And Interest Expense Transactions Of Other Parties For Which The Company Is Trustee. These do not represent tax liabilities, penalties, or payments for the Company. This disclosure is representing an item between the IRS and a Trust Client in which the Bank acts as a Trustee. These numbers do not reflect any tax owed, due, or payable from the Corporation.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration